Connector assemblies of this general type are now commonly used for connecting subscribers telephone apparatus to the public network; use of a socket and plug allowing easy movement or replacement of the telephone. For such use plugs and sockets having 4 or 6 terminals in plugs and sockets of the same overall sizes are usually used. Such assemblies can be easily mass produced using injection moulding and automatic assembly techniques. However, there is now a considerable need for a series of electrical connectors of the same general type having a larger number of terminals. This is particularly so in the telecommunications and computer related fields.
In producing a series of connectors having a varying number of terminals it is convenient for the various members of the series to differ only in the width of the engageable portion of the plug and the corresponding socket recess. This can lead to smaller plugs being inadvertently inserted into larger sockets which can result in damage to either or both of the pieces of equipment so connected. Even if plugs and sockets of the same size are being connected it is often desirable to prevent plugs intended for a particular purpose from being inserted into sockets of the same size intended for some other purpose. Keying systems to prevent both such mismatchings are known but involve the use of a number of complicated systems each requiring many keys and keyways to avoid any mismatching of plugs and sockets. Such systems also require an overly complicated series of moulds.